Combining ability of seven silk technological characters in mulberry silkworm,Bombyx mori

Abstract

The combining ability (abbreviated, CA) effects of five races (KA, CC1, CA2, NB4D2 and NB18) of mulberry silkworm Bombyx morí and their 20 F 1 's, including reciprocals, were analyzed in a 5x5 diallelic crossing system for the following seven silk technological characters: cocoon weight, shell weight, cocoon shell ratio, raw silk percentage, silk filament length, silk reelability and silk neatness. The parental race CA2 did not show the best general CA for any of these seven characters, whereas the other parental races did for different characters as follows: race KA for raw silk percentage, silk filament length, silk reelability and silk neatness; race CCI for cocoon weight, shell weight, and cocoon shell ratio; race NB4D2 for cocoon weight, raw silk percentage; race NB18 for cocoon shell ratio. Values of race CA2 for general CA were negative for cocoon weight, shell weight, cocoon shell ratio and raw silk percentage, and were low for silk filament length, silk reelability and silk neatness. This indicated a poor performance of this race in hybrid combinations with the remaining races. The results of specific CA effects suggested the restricted use of race CA2 as a female parent in hybrid combinations with males of races NB18 or NB4D2. Crosses CA2 x NB4D2 and CA2 x NB18 showed the desired positive specific CA effects for all characters except silk reelability and silk neatness, respectively. Cross CCI x NB4D2 showed desired positive specific CA effects for all characters. Variances of general and specific CA revealed that the non-additive type of gene control plays a predominant role in the inheritance of all the seven characters analyzed. The races and crosses showing best values of general and specific CA effects will be used in future breeding programmes.

Combining Ability Analysis of Four Ecoraces and C2 Breed of Eri Silkworm, Samia Ricini Donovan

“…Specific combining ability analysis is a useful tool for the identification of superior hybrids to exploit hybrid vigour for increasing silk production and it involves both dominance and other interactions which together constitute the non-additive type of gene action which could be optimized in upgrading the genetic potential of the crop by adopting reciprocal recurrent selection. Predominant role of non-additive gene action for cocoon weight and cocoon shell weight has been studied in mulberry silkworm, Bombyx mori (Bhargava et al, 1992;1995). Among ten reciprocal crosses, GYP X TGBP showed significant reciprocal effects for six traits viz., hatching, larval weight, cocoon weight, shell weight, shell percentage and absolute silk yield followed by GYP X C2 for two traits viz., fecundity and cocoon weight.…”

Mating compatibility and offspring traits evaluation among different strains of Tenebrio molitor

“…Along the same lines, Doddaswamy et al ( 2009 ), while experimenting with inbred and outbred crosses of B. mori , reported that F1 hybrids of outbred crosses performed better in terms of specific economic traits, such as tightly formed shells of spun cocoons, uniform growth, and consistent crop performance, compared to inbred crosses. Similarly, Bhargava et al ( 1995 ) tested the cross-breeding of five B. mori races and reported differences for seven silk technological characters; the weight of cocoon and shell, cocoon shell ratio, percentage of raw silk, length of silk filament, silk reliability, as well as silk neatness. However, cross-breeding only sometimes results in improving all economically valuable traits.…”

“…Cross-breeding has successfully applied though in other insect species. Indicatively, in the sector of sericulture, researchers utilized divergent parental strains of the silkworm Bombyx mori (L.) (Lepidoptera: Bombycidae) and produced hybrids with better economic traits and technological characteristics (Bhargava et al 1995 ; Doddaswamy et al 2009 ; Reddy et al 2010 ).…”

Identifying parents and generating hybrids with high combining ability for yielding fresh cocoon and raw silk in silkworm (Bombxy mori L.)

“…Genetic parameters including general combining ability (GCA) and special combining ability (SCA) and heterosis, for important characters in pure lines and hybrids, are effective for improvement (Bhargava et al, 1995;Seidavi et al, 2004). For that, selected lines are crossed with a set of testers (line × tester) to evaluate GCA, SCA, and genetic parameters (Singh et al, 1990;Islam et al, 2005).…”